1. Field
Some embodiments of the invention relate generally to communication systems and particularly to internet protocol multimedia subsystem (IMS) communication systems. Certain embodiments also generally relate to supporting single radio voice call continuity and reverse single radio voice call continuity.
2. Description of the Related Art
A voice call initiated by a user equipment (UE) that is anchored in IMS can be persisted as the UE moves between circuit switched (CS) radio domains and packet switched (PS) radio domains, and vice-versa. For example, a voice call initiated by a UE within a third generation partnership project (3GPP) second-generation (2G) or third-generation (3G) telecommunication system can be handed over to a 3GPP long term evolution (LTE)-advanced communication system, and vice-versa.
As a more specific example, a voice call that is anchored in IMS can be initiated by a UE within a 3GPP universal terrestrial radio access network (UTRAN)/global system for mobile communications (GSM) enhanced data rates for GSM (EDGE) radio access network (GERAN) CS telecommunication system and handed over to an IMS over evolved universal terrestrial radio access network (e-UTRAN)/high speed packet access (HSPA) telecommunication system, and vice-versa. Voice call continuity from an IMS over EUTRAN/HSPA telecommunication system to a UTRAN/GERAN telecommunication system for voice calls that are anchored in IMS when the UE is capable of transmitting/receiving only one of those telecommunication systems at a given time is referred to as single radio voice call continuity (SRVCC). Voice call continuity from a UTRAN/GERAN telecommunication system to an IMS over E-UTRAN/HSPA telecommunication system for voice calls that are anchored in IM when the UE is capable of transmitting/receiving on only one of those telecommunication systems at a given time is referred to as reverse single radio voice call continuity (rSRVCC).